SerialPort class sample using boost::asio::serial_port

sample_main.cpp

#include "stdafx.h"
#include "SerialPort.h"

int main(int argc, char* argv[])
{
	bool rv;

	SerialPort::print_devices();
	std::string name = SerialPort::get_port_name(0);

	SerialPort serial;
	rv = serial.start(name.c_str(), 115200);	
	if (rv == false) {
		return -1;
	}

	// initialize
	serial.end_of_line_char(0x0d);
	serial.write_some("BI010\r\n");
	serial.write_some("PE011\r\n");
	serial.write_some("RA01000\r\n");

	// wait
	Sleep(5 * 1000);

	serial.stop();

	return 0;
}

SerialPort.cpp

#include "StdAfx.h"

#include <Setupapi.h>
#pragma comment(lib, "Setupapi.lib")

#include "SerialPort.h"

SerialPort::SerialPort(void) : end_of_line_char_('\n')
{
}

SerialPort::~SerialPort(void)
{
	stop();
}

char SerialPort::end_of_line_char() const
{
	return this->end_of_line_char_;
}

void SerialPort::end_of_line_char(const char &c)
{
	this->end_of_line_char_ = c;
}

std::vector<std::string> SerialPort::get_port_names()
{
	std::vector<std::string> names;

	BOOL rv;
	DWORD size;
	GUID guid[1];
	HDEVINFO hdevinfo;
	DWORD idx = 0;
	SP_DEVINFO_DATA devinfo_data;
	devinfo_data.cbSize = sizeof(SP_DEVINFO_DATA);
	int count = 0;

	rv = SetupDiClassGuidsFromName("Ports", (LPGUID)&guid, 1, &size) ;
	if (!rv) {
		std::cout << "error : SetupDiClassGuidsFromName() failed..." << std::endl;
		return names;
	}

	hdevinfo = SetupDiGetClassDevs(&guid[0], NULL, NULL, DIGCF_PRESENT | DIGCF_PROFILE);
	if (hdevinfo == INVALID_HANDLE_VALUE) {
		std::cout << "error : SetupDiGetClassDevs() failed..." << std::endl;
		return names;
	}

	while(SetupDiEnumDeviceInfo(hdevinfo, idx++, &devinfo_data)) {
		char friendly_name[MAX_PATH];
		char port_name[MAX_PATH];
		DWORD prop_type;
		DWORD type = REG_SZ;
		HKEY hKey = NULL;

		rv = ::SetupDiGetDeviceRegistryProperty(hdevinfo, &devinfo_data, SPDRP_FRIENDLYNAME, &prop_type,
			                                    (LPBYTE)friendly_name, sizeof(friendly_name), &size);
		if (!rv) {
			std::cout << "error : SetupDiGetDeviceRegistryProperty() failed..." << std::endl;
			continue;
		}

		hKey = ::SetupDiOpenDevRegKey(hdevinfo, &devinfo_data, DICS_FLAG_GLOBAL, 0, DIREG_DEV, KEY_READ);
		if (!hKey) continue;
	
		size = sizeof(port_name);
		rv = ::RegQueryValueEx(hKey, "PortName", 0, &type, (LPBYTE)&port_name, &size);
		::RegCloseKey(hKey);
	
		names.push_back(port_name);
	}

	SetupDiDestroyDeviceInfoList(hdevinfo);

	return names;
}

int SerialPort::get_port_number()
{
	std::vector<std::string> names = get_port_names();
	return names.size();
}

std::string SerialPort::get_port_name(const unsigned int &idx)
{
	std::vector<std::string> names = get_port_names();
	if (idx >= names.size()) return std::string();
	return names[idx];
}

void SerialPort::print_devices()
{
	std::cout << "SerialPort::print_devices()" << std::endl;
	int n = SerialPort::get_port_number();
	for (int i = 0; i < n; ++i) {
		std::string name = SerialPort::get_port_name(i);
		std::cout << "\t" << name.c_str() << std::endl;
	}
}

bool SerialPort::start(const char *com_port_name, int baud_rate)
{
	boost::system::error_code ec;

	if (port_) {
		std::cout << "error : port is already opened..." << std::endl;
		return false;
	}

	port_ = serial_port_ptr(new boost::asio::serial_port(io_service_));
	port_->open(com_port_name, ec);
	if (ec) {
		std::cout << "error : port_->open() failed...com_port_name="
			<< com_port_name << ", e=" << ec.message().c_str() << std::endl; 
		return false;
	}

	// option settings...
	port_->set_option(boost::asio::serial_port_base::baud_rate(baud_rate));
	port_->set_option(boost::asio::serial_port_base::character_size(8));
	port_->set_option(boost::asio::serial_port_base::stop_bits(boost::asio::serial_port_base::stop_bits::one));
	port_->set_option(boost::asio::serial_port_base::parity(boost::asio::serial_port_base::parity::none));
	port_->set_option(boost::asio::serial_port_base::flow_control(boost::asio::serial_port_base::flow_control::none));

	boost::thread t(boost::bind(&boost::asio::io_service::run, &io_service_));

	async_read_some_();

	return true;
}

void SerialPort::stop()
{
	boost::mutex::scoped_lock look(mutex_);

	if (port_) {
		port_->cancel();
		port_->close();
		port_.reset();
	}
	io_service_.stop();
	io_service_.reset();
}

int SerialPort::write_some(const std::string &buf)
{
	return write_some(buf.c_str(), buf.size());
}

int SerialPort::write_some(const char *buf, const int &size)
{
	boost::system::error_code ec;

	if (!port_) return -1;
	if (size == 0) return 0;

	return port_->write_some(boost::asio::buffer(buf, size), ec);
}

void SerialPort::async_read_some_()
{
	if (port_.get() == NULL || !port_->is_open()) return;

	port_->async_read_some( 
		boost::asio::buffer(read_buf_raw_, SERIAL_PORT_READ_BUF_SIZE),
		boost::bind(
			&SerialPort::on_receive_,
			this, boost::asio::placeholders::error, 
			boost::asio::placeholders::bytes_transferred));
}

void SerialPort::on_receive_(const boost::system::error_code& ec, size_t bytes_transferred)
{
	boost::mutex::scoped_lock look(mutex_);

	if (port_.get() == NULL || !port_->is_open()) return;
	if (ec) {
		async_read_some_();
		return;
	}

	for (unsigned int i = 0; i < bytes_transferred; ++i) {
		char c = read_buf_raw_[i];
		if (c == end_of_line_char_) {
			this->on_receive_(read_buf_str_);
			read_buf_str_.clear();
		}
		else {
			read_buf_str_ += c;
		}
	}

	async_read_some_();
}

void SerialPort::on_receive_(const std::string &data)
{
	std::cout << "SerialPort::on_receive_() : " << data << std::endl;
}

SerialPort.h

#pragma once

#include <boost/asio.hpp>
#include <boost/asio/serial_port.hpp>
#include <boost/system/error_code.hpp>
#include <boost/system/system_error.hpp>
#include <boost/bind.hpp>
#include <boost/thread.hpp>

#include <string>
#include <vector>

typedef boost::shared_ptr<boost::asio::serial_port> serial_port_ptr;

#define SERIAL_PORT_READ_BUF_SIZE 256

class SerialPort
{
protected:
	boost::asio::io_service io_service_;
	serial_port_ptr port_;
	boost::mutex mutex_;
	
	char read_buf_raw_[SERIAL_PORT_READ_BUF_SIZE];
	std::string read_buf_str_;

	char end_of_line_char_;

private:
	SerialPort(const SerialPort &p);
	SerialPort &operator=(const SerialPort &p); 

public:
	SerialPort(void);
	virtual ~SerialPort(void);

	char end_of_line_char() const;
	void end_of_line_char(const char &c);

	virtual bool start(const char *com_port_name, int baud_rate=9600);
	virtual void stop();

	int write_some(const std::string &buf);
	int write_some(const char *buf, const int &size);

	static int get_port_number();
	static std::string get_port_name(const unsigned int &idx);
	static std::vector<std::string> get_port_names();
	static void print_devices();

protected:
	virtual void async_read_some_();
	virtual void on_receive_(const boost::system::error_code& ec, size_t bytes_transferred);
	virtual void on_receive_(const std::string &data);

};

Please use comments to show us, what your code is doing. thx.

Hi, thanks for this example. I ran into a serious bug in start() which stopped it ever receiving data because io_service_.run() was returning before it was given any work to do. The fix is to call async_read_some_(); before creating the thread and calling run():

`bool SerialPort::start(const char *com_port_name, int baud_rate)
{
boost::system::error_code ec;

if (port_) {
	std::cout << "error : port is already opened..." << std::endl;
	return false;
}

port_ = serial_port_ptr(new boost::asio::serial_port(io_service_));
port_->open(com_port_name, ec);
if (ec) {
	std::cout << "error : port_->open() failed...com_port_name="
		<< com_port_name << ", e=" << ec.message().c_str() << std::endl; 
	return false;
}

// option settings...
port_->set_option(boost::asio::serial_port_base::baud_rate(baud_rate));
port_->set_option(boost::asio::serial_port_base::character_size(8));
port_->set_option(boost::asio::serial_port_base::stop_bits(boost::asio::serial_port_base::stop_bits::one));
port_->set_option(boost::asio::serial_port_base::parity(boost::asio::serial_port_base::parity::none));
port_->set_option(boost::asio::serial_port_base::flow_control(boost::asio::serial_port_base::flow_control::none));

async_read_some_();
std::thread t( [this] () {this->io_service_.run(); });
thread_.swap(t);

return true;

}

void SerialPort::stop()
{
std::unique_lock lock(mutex_);

if (port_) {
	port_->cancel();
	port_->close();
	port_.reset();
}

if (thread_.joinable())
thread_.join();

io_service_.stop();
io_service_.reset();

}
`

Quick question on your reply. In this bit:

async_read_some_();
std::thread t( [this] () {this->io_service_.run(); });
thread_.swap(t);

then

if (thread_.joinable())
thread_.join();

Am I right in thinking that thread_ is a member variable of the class?

perfect!

Thank you for this excelent example.
Just one minor suggestion: io_service_.restart() needs to be called in function SerialPort::start if there has been a previous call to SerialPort::stop, where io_service_.reset() is invoked. like this:

bool SerialPort::start(const char *com_port_name, int baud_rate)
{
	boost::system::error_code ec;

	if (port_) {
		std::cout << "error : port is already opened..." << std::endl;
		return false;
	}

        io_service_.restart();

	port_ = serial_port_ptr(new boost::asio::serial_port(io_service_));
	port_->open(com_port_name, ec);
        ...

otherwise, it stops working on subsequent calls to stop() / start().